The polar headgroup of the detergent governs the accessibility to water of tryptophan octyl ester in host micelles
Autor: | Béatrice de Foresta, Jacques Gallay, Michel Vincent, Ludovic Tortech, Christine Jaxel |
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Rok vydání: | 2001 |
Předmět: |
Detergent micelle
Surface Properties Phosphorylcholine Iodide Detergents Dodecylmaltoside Biophysics Quantum yield Micelle Biochemistry Fluorescence spectroscopy Polyethylene Glycols chemistry.chemical_compound Glucosides Octa(ethylene glycol) dodecyl monoether Collisional quencher Organic chemistry Micelles Fluorescent Dyes chemistry.chemical_classification Quenching (fluorescence) Molecular Structure Tryptophan octyl ester Tryptophan Membrane Proteins Water Cell Biology Hydrogen-Ion Concentration Dodecylphosphocholine Fluorescence Crystallography chemistry Acrylamide Anisotropy Ethylene glycol |
Zdroj: | Biochimica et Biophysica Acta (BBA) - Biomembranes. 1514(1):76-86 |
ISSN: | 0005-2736 |
DOI: | 10.1016/s0005-2736(01)00370-4 |
Popis: | Many attempts have been made to rationalize the use of detergents for membrane protein studies [J. Biol. Chem. 264 (1989) 4907]. The barrier properties of the detergent headgroup may be one parameter critically involved in protein protection. In this paper, we analyzed these properties using a model system, by comparing the accessibility of tryptophan octyl ester (TOE) to water-soluble collisional quenchers (iodide and acrylamide) in three detergent micelles. The detergents used differed only in the chemical nature of their polar headgroups, zwitterionic for dodecylphosphocholine (DPC) and nonionic for octa(ethylene glycol) dodecyl monoether (C(12)E(8)) and dodecylmaltoside (DM). In all cases, in phosphate buffer at pH 7.5, the binding of 5 microM TOE was complete in the presence of a slight excess of detergent micelles over TOE molecules, resulting in a significant blue shift and greater intensity of TOE fluorescence emission. The resulting quantum yield of bound TOE was between 0.08 (in DPC) and 0.12 (in DM) with an emission maximum (lambda(max)) of approximately 335 nm whatever the detergent micelle. Time-resolved fluorescence intensity decays of TOE at lambda(max) were heterogeneous in all micelles (3-4 lifetime populations), with mean lifetimes of 1.7 ns in DPC, and 2 ns in both C(12)E(8) and DM. TOE fluorescence quenching by iodide, in detergent micelles, yielded linear Stern-Volmer plots characteristic of a dynamic quenching process. The accessibility of TOE to this ion was the greatest with C(12)E(8), followed by DPC and finally DM (Stern-Volmer quenching constants K(sv) of 2 to 5.5 M(-1)). In contrast, the accessibility of TOE to acrylamide was greatest with DPC, followed by C(12)E(8) and finally DM (K(sv)=2.7-7.1 M(-1)). TOE also presents less rotational mobility in DM than in the other two detergents, as shown from anisotropy decay measurements. These results, together with previous TOE quenching measurements with brominated detergents [Biophys. J. 77 (1999) 3071] provide reference data for analyzing Trp characteristics in peptide (and more indirectly protein)-detergent complexes. The main finding of this study was that TOE was less accessible (to soluble quenchers) in DM than in DPC and C(12)E(8), the cohesion of DM headgroup region being suggested to play a role in the ability of this detergent to protect function and stability of solubilized membrane proteins. |
Databáze: | OpenAIRE |
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